Boosting a signal-to-interference ratio of a mobile station

ABSTRACT

In a cell of a cellular wireless communication system, the SIR of at least one user in a sector of the cell is altered by temporarily reducing transmissions on a forward link in at least one other sector of the cell or a sector in another cell in accordance with a pattern.

BACKGROUND

[0001] This invention relates to boosting a signal-to-interference ratioof a mobile station.

[0002] In our discussion, we use the following acronyms: MS MobileStation BS Base Station CDMA Code Division Multiple Access FDMAFrequency Division Multiple Access TDMA Time Division Multiple AccessSIR Signal to Interference Ratio HARQ Hybrid ARQ ARQ Automatic RepeatRequest GSM Groupe Speciale Mobile of the European TelecommunicationStandards Institute. AMPS Advanced Mobile Phone Service CDMA 2000 Thirdgeneration CDMA standard for mobile wireless communication. 1xEV-DO 1xEvolution Data Only standard. 3GPP2 Third Generation Partnership Project2

[0003] In a wireless communication system, limited available resourcessuch as frequency and time are shared among the users of the system. Asshown in FIG. 1, in a cellular system 10, a covered area is divided intocells 12, and each cell is served by a base station (BS) 14. To increasecapacity for a given frequency spectrum being used, a BS's service areamay be further divided into sectors 16, for example, three sectors,using directional antennas, as described in T. S. Rappaport, WirelessCommunications. Prentice Hall, 1996. Some cellular systems, such as TDMA(GSM, IS-54) and FDMA (AMPS), use so-called frequency reuse or frequencyplanning to increase communication capacity.

[0004] In a frequency reuse system, the same frequency channels arereused in multiple cells. In FIG. 1, for example, all three cells 12,13, 15 have sectors 16, 18, 20 that bear a given letter (e.g., theletter “C”) indicating that they use the same frequency channel.

[0005] Frequency reuse helps users at cell edges, for example, user 22,located at the edge 24 of a cell to achieve a better signal tointerference ratio (SIR).

[0006] As more and more carrier frequencies are used for frequencyreuse, the SIRs of the users in a given cell get better and the SIRdistribution among users of the cell gets more even. However, thespectral efficiency gets lower, which will result in lower total systemcapacity for a given total spectrum.

[0007] CDMA systems such as IS-95A/B, CDMA-2000, and 1xEV-DO incorporatemaximal frequency reuse in which neighboring cells use the same carrierfrequency, i.e., the reuse factor (defined as the number of frequencychannels used)=1. Different codes are used to differentiate differentcells. This system yields good spectral efficiency, but the SIRdistribution within a cell can be uneven depending on the location ofthe user.

[0008] The SIR of a user at a given location is determined by thelocations and configurations (e.g., omni cell or three-sectored cell) ofthe cells. The SIR in turn determines the instantaneous communicationrate of the user.

[0009] Recently, 3GPP2 approved a new wireless packet data air interfacestandard called IS-856, sometimes also referred to as 1xEV-DO. IS-856provides the capability to support high-speed wireless Internetcommunication at speeds up to 2.45 Mbit/s using only 1.25 MHz spectrum.

[0010]FIG. 2 shows an example, for 1xEV-DO, of the percentagedistribution of forward link rates of users who are uniformlydistributed geographically within a three-sectored cell. As can be seenfrom the figure, the lowest and highest rates, 38.4 kbps and 2.4 Mbps,differ by a factor of 64. This large difference in rate makes it hard toachieve an even throughput to all users in a cell, as is required forconstant bit-rate applications such as voice. For data applications, acertain degree of unfairness, e.g., giving higher throughput for userswho are close to the BS and lower throughput for users who are far fromthe BS, is allowed as long as it does not violate certain fairnessconditions.

[0011] Because the forward link of 1xEV-DO is TDMA, it is possible toallocate different amounts of time for each user to increase thefairness, i.e., by giving more time slots for low SIR users and fewertime slots for high SIR users. However, this will lower the throughputof the overall system because low SIR users will consume a large shareof the resources. Systems designed to increase fairness tend to reducesector throughput.

SUMMARY

[0012] In general, in one aspect, the invention features a method thatincludes in a cell of a cellular wireless communication system, alteringthe SIR of at least one user in a sector of the cell by temporarilyreducing transmissions on a forward link in at least one other sector ofthe cell or a sector in another cell in accordance with a pattern.

[0013] Implementations of the invention may include one or more of thefollowing features. The pattern is organized in a sequence of timeslots, and the pattern defines which of the sectors has transmissionsturned on or off in each of the time slots. The pattern comprises apredetermined fixed pattern that is repeated as time passes. A currentstate of transmissions is determined in at least one of the sectors ofthe cell or a sector in another cell, and the pattern is set dynamicallybased on the determined state of the transmissions. The current state oftransmissions includes the scheduling status of transmissions inneighboring sectors in the cell or in one or more other sectors in oneor more other cells. Neighboring sectors include other sectors in thecell and sectors in some other cells. The current state of transmissionsincludes the transmission rates of some neighbor sectors. The currentstate of transmissions includes the next time slot usage. The currentstate of transmissions includes the forward link SIR. The current stateof transmissions includes user location. The current state oftransmissions includes a fairness setting. The current state oftransmissions includes an application type of user and/or QoS. Thetransmissions are temporarily reduced by turning transmissions on andoff in selected sectors according to the pattern. The pattern includesturning off transmissions in other sectors more frequently to help usershaving lower communication rates. A frequency reuse factor of one orhigher is used in the wireless system. The wireless system comprises1xEV-DO.

[0014] In general, in another aspect, the invention features apparatusthat includes (a) wireless transmission facilities for more than onesector of a cell, and (b) control facilities connected to the wirelesstransmission facilities and configured to alter the SIR of at least oneuser in a sector of the cell by temporarily reducing transmissions on aforward link in at least one other sector of the cell or a sector inanother cell in accordance with a pattern. Implementations of theinvention may include one or more of the following features. The controlfacilities comprise sector controllers for controlling the wirelesstransmission facilities for the respective sectors.

[0015] In general, in another aspect, the invention features a mediumbearing intelligence configured to enable a machine to effect theactions that comprise: in a cell of a cellular wireless communicationsystem, altering the SIR of at least one user in a sector of the cell bytemporarily reducing transmissions on a forward link in at least oneother sector of the cell or a sector in another cell in accordance witha pattern.

[0016] In general, in another aspect, the invention features apparatusthat includes a sector controller adapted to control transmissions in asector of a cell of a wireless communication system and to communicatewith other sector controllers in the cell or in one or more other cellsto coordinate the turning on and off of transmissions in at least one ofthe sectors based on the transmission state in at least another one ofthe sectors.

[0017] Other advantages and features will become apparent from thefollowing description and from the claims.

DESCRIPTION

[0018]FIG. 1 shows frequency or time reuse factor of three.

[0019]FIG. 2 shows a bar chart of rate distribution for frequency ortime reuse factor of one.

[0020]FIG. 3 shows a bar chart of a rate distribution for frequency ortime reuse factor of three.

[0021]FIG. 4 shows a three-sectored base station

[0022] Here, we propose a system in which some BS's turn off theirtransmissions in forward links to boost the SIR of a user in a badlocation and thereby achieve good rates and more even rates among usersin a cell. By employing this technique, the system can achieve a moreconcentrated rate distribution (less variance in the rate) than shown inFIG. 2 and thereby can provide more even throughput to users andincrease the sum of throughput of all users in a sector, i.e., thesector throughput.

[0023] This system can be thought of as a time reuse system in whichdifferent sectors use different time slots to boost SIR of users in therespective sectors. Unlike a frequency reuse system, the time reusepattern can be easily adjusted dynamically based on an SIR measurement,the location of the user, the application type being run on the user'sdevice, or configuration data such as a fairness setting, e.g., asetting that guarantees a certain limit on the ratio of the maximum andminimum user throughput or a minimum throughput. Also, the time reusepattern may be disabled easily.

[0024] Although we shall explain the benefits of time divisionmultiplexing among sectors in the context of an example that concerns1xEV-DO systems, benefits can be achieved in other wireless systems,including TDMA, CDMA, and OFDM systems.

[0025] Let M be the number of sectors in a cell. We assume a frequencyreuse factor of one, i.e., every sector in a cell uses the samefrequency. We assume that the same number, K, of active MSs areoperating in each sector. The analysis can be generalized to cover casesin which different numbers of MSs are operating in respective sectors.

[0026] We assume each MS chooses the best serving sector from which todownload data, although, in reality, there can be some delay inswitching sectors.

[0027] We consider two cases of time reuse: fixed and adaptive. In afixed time reuse pattern, sectors are turned off at times that aredefined by a pre-determined pattern. In an adaptive reuse pattern, thetiming of the turning off of sectors depends on the status of the systemsuch as the next time slot usage in each sector. For example, when alow-rate user is using the next time slot in a sector, some neighborsectors can be turned off during the slot to help the disadvantageduser.

[0028] Fixed Reuse Pattern

[0029] Let S be a local group of sectors in a cell whose transmissionstates (on and off) will be controlled jointly. S could be fewer thanall of the sectors in the cell. Assume that the pattern of on and offstates is repeated in successive control periods, and that each controlperiod includes a number L of time slots. Let Si be the set of sectorsallowed to transmit in the time slot Ti, where i=1, . . . , L. Such apattern is illustrated in the following table for the case of foursectors in S and four time slots. The lengths of time slots Ti's can bedifferent in general. T1 T2 T3 T4 Sector 1 On Off On Off Sector 2 Off OnOn Off Sector 3 On Off Off On Sector 4 Off On Off On

[0030] In this example, S={Sectors 1, 2, 3, and 4}, S1={Sectors 1 and3}, S2={Sectors 2 and 4}, S3={Sectors 1 and 2}, and S4={Sectors 3 and4}.

[0031] Another example is shown in FIG. 1, where S contains threesectors in a cell, S1={A}, S2={B}, S3={C}, and there are three timeslots T1=T2=T3=T.

[0032] In FIG. 3, we show the percentage distribution of users by ratefor this case, representing a clear improvement in the throughputcompared to the distribution of FIG. 2. (Because each of the sectors isactive only for ⅓ of the time, the throughput needs to be scaled down bya factor of 3.)

[0033] We use two quantities to measure performance. We define theequal-time throughput E[R], where R is the instantaneous rate, per cellper carrier as the expected cell throughput per carrier (the 1.25 MHzband in case of 1xEV-DO), i.e., the average rate of a user randomlylocated in the sector. This is the cell throughput per carrier under thecondition that every user gets the same amount of serving time. Wedefine the equal-data throughput 1/E[1/R] per cell per carrier as theexpected cell throughput per carrier when each user downloads the sameamount of data independent of its channel condition, which is equal tothe inverse of the expected value of the inverse of the rate R. Thesethroughput values will be scaled down by the reuse factor to include theeffect of reduced time usage due to time reuse.

[0034] In the example above (FIG. 1), we get the following simulationresults assuming 19 hexagonal three-sectored cells: E[R] 1/E[1/R] FIG.Time reuse = 1 2923 kbps 1520 kbps 2 Time reuse = 3 2105 kbps 1864 kbps3 Gain −28% 23%

[0035] Although we loose 28% in equal-time throughput, we gain 23% inequal-data throughput when the time reuse=3 is used. Therefore, the timereuse of three in this example improves performance of systems with highfairness among users.

[0036] In 1xEV-DO, even when the data portion of a time slot is empty,the pilot portion is transmitted. The MS then determines its DRC (DataRate Control, i.e., the rate at which the MS asks a sector to send datain the forward link) based on the pilot only. Therefore, even when thedata portions of time slots from interfering sectors are empty, andtherefore the MS could receive at high rate, its DRC will still be low.Even though the BS normally would transmit to the sector at the rate(here, the low rate) that the MS has requested, it is still possible totake advantage of the boosted channel condition that time reuseprovides. For example, 1xEV-DO uses HARQ, which permits the MS to sendan ACK signal to alert the sector to stop transmission of the remainingslots of multi-slot packets and thereby effectively increase thetransmission rate.

[0037] Adaptive Reuse Pattern

[0038] Forward link capacity can be improved by a time reuse scheme thatis adaptive. Let I={I_(i)|i=1, . . . , M−1 represent the set ofinterferences from other sectors, where I_(i) denotes the ratio of theinterference from the i-th sector to the power from the serving sectorfor a user (the serving sector is the sector from which the user isreceiving packets), M>>1 is the total number of sectors. Let N denotethe ratio of the noise to the power in the serving sector. We assumeI_(i) and N are random variables that depend on the user location andshadow fading. To simplify the derivation, we assume no Rayleigh fading(thus no multi-user diversity gain).

[0039] Then, channel capacity C is given by${C = {{\log_{2}( {1 + \frac{1}{N + I_{A}}} )}\quad\lbrack {{b/s}/{Hz}} \rbrack}},$

[0040] where I_(A)=sum(I_(i), i=1, . . . , M−1) is the aggregateinterference from other sectors.

[0041] Let m=m(I_(A)) be the number of other sectors with largestI_(i)'s to be turned off during transmission for the current user. m isa random variable that depends on I_(A) (or equivalently the DRC of theuser with a little less accuracy). m could be a function of I_(i)'s ingeneral, but that could make the system too complicated.

[0042] Let q(N,I) be the relative serving time for a user characterizedby {N,I}, i.e., E[q(N,I)]=1. For example, for Qualcomm's fairproportional scheduler (Qualcomm, 1xEV Scheduler: Implementation of theProportional Fair Algorithm, Application Note, 80-85573-1 X5, Jun. 27,2001), if all queue's are backlogged, or when each user receives datawhose amount is proportional to its supportable rate, then q(N,I)=1. Ifevery user has the same amount of data to receive, thenq(N,I)=1/R(N,I)/E[1/R(N,I)], where R(N,I) is the rate supportable at{N,I}. We simply denote q(N,I) by q and call it the user bandwidthvector.

[0043] Let α denote${\frac{E\lbrack q\rbrack}{E\lbrack {q( {m + 1} )} \rbrack} = \frac{1}{E\lbrack {q( {m + 1} )} \rbrack}},$

[0044] which is the average fraction of time a sector is turned onduring the period assuming there is no sector with an empty queue. Thechannel capacity C′ of this time reuse scheme becomes:${C^{\prime} = {\alpha \quad {{\log_{2}( {1 + \frac{1}{N + {\beta ( {I_{A} - I_{m}} )}}} )}\quad\lbrack {{b/s}/{Hz}} \rbrack}}},$

[0045] where I_(m)=sum of m largest I_(i)'s. 0≦β≦1 is the factor thatreduces the interference as a bonus of turning off some sectors. Thatis, turning off some sectors not only reduces the interference I_(A) byI_(m), but also reduces the interference further because other sectorsare also turned off during the period. Because there is no HARQ for highrate packets, i.e., one-slot packets with rates 1842.3 or 2457.6 kbps,these rates will not usually benefit from the reduced β. This effectwould produce only a minor degradation on R′ when q′ is inverselyproportional to R′. If there is an adaptive DRC estimation algorithmemployed in MSs that can estimate the increased SNR due to some silentsectors, the 1843.2 kbps rate would benefit, i.e., it could become2457.6 kbps sometimes.

[0046] If we make the unrealistic assumption that sectors are perfectlycoordinated so that when a sector needs to be turned off in the nexttime slot to boost the SIR of a MS, it does not have any packet to sendin the slot, we get β=α. Because there is some correlation in the timeswhen neighbor sectors are turned off, β would usually be slightly largerthan α. The difference would widen (slightly) if m is large becauseother sectors will have less chance to be turned off in that m sectorsare already turned off and there is no traffic in those m sectors.However, E[β] would be close to α. Therefore, we assume β=α.

[0047] Analysis and Simulation Results

[0048] Because channel capacity increases only logarithmically at largeSNR, and the adaptive reuse technique does not help high ratecommunications, we arrange to turn off sectors only for users with lowrates. Using a low-SNR approximation, we get the achievable rate R,i.e., $\begin{matrix}{{R \approx {\lambda \quad {\frac{1}{N + I_{A}}\quad\lbrack {{b/s}/{Hz}} \rbrack}}},} & (1)\end{matrix}$

[0049] where λ≈0.5 at rates 38.4˜1228.8 Kbps and λ≈0.25 at rates1843.2˜2457.6 Kbps in a 1xEV-DO system. Because we are not attemptingany improvement for high rate users, we can safely assume λ=0.5 for theanalysis of the throughput improvement for low-rate users.

[0050] The improved rate R′ becomes$R^{\prime} \approx {\lambda \quad {{\frac{\alpha}{N + {\beta ( {I_{A} - I_{m}} )}}\quad\lbrack {{b/s}/{Hz}} \rbrack}.}}$

[0051] This approximation will be accurate if the improved SNR=$\frac{1}{N + {\beta ( {I_{A} - I_{m}} )}}$

[0052] is less than about two, i.e., we can still assume λ=0.5. We use$\alpha = \frac{1}{E\lbrack {q^{\prime}( {m + 1} )} \rbrack}$

[0053] for the adaptive reuse case, since q′ depends on the improved R′in general.

[0054] Based on the user bandwidth vectors q and q′ for the originalcase (time reuse=1) and the adaptive reuse case, we get the sectorthroughputs S=E[q R] and S′=E[q′ R′] for the original case and theadaptive reuse case, respectively. In the following throughput analysis,we demonstrate how much gain we can get using adaptive reuse.

[0055] Case I (Time Reuse=1)

[0056] For case I, q=1/R/E[1/R] and q′=1/R′/E[1/R′]

[0057] In this case, we assume β=α. S and S′ become$S \approx {\frac{1}{{E\lbrack {N/\lambda} \rbrack} + {E\lbrack {I_{A}/\lambda} \rbrack}}\quad {and}}$$S^{\prime} \approx {\frac{1}{{{E\lbrack {N/\lambda} \rbrack}/\alpha} + {E\lbrack {I_{A}/\lambda} \rbrack} - {E\lbrack {I_{m}/\lambda} \rbrack}}.}$

[0058] If N is sufficiently small (if not coverage limited, i.e., cellsizes are small), then S′ will be always greater than S. Although λdepends on the rate R and R′ for the original and the adaptive cases,respectively, we simply assume λ is a function of R because we are notattempting to increase R′ for high rate users and in this case λ isalmost constant anyway.

[0059] Assuming N=0, we get$\alpha = {\frac{E\lbrack {( {I_{A} - I_{m}} )/\lambda} \rbrack}{E\lbrack {( {I_{A} - I_{m}} ){( {m + 1} )/\lambda}} \rbrack}.}$

[0060] In this case, the throughput gain g=S′/S becomes$g = {\frac{E\lbrack {I_{A}/\lambda} \rbrack}{E\lbrack {( {I_{A\quad} - I_{m}} )/\lambda} \rbrack}.}$

[0061] We assume hexagonal three-sectored cells, an antenna patterndefined in the 1xEV-DV evaluation methodology document (3GPP2, 1xEV-DVEvaluation Methodology-Addendum (V5)), and shadow fading of 8.9 dB withbase station correlation of 0.5. We randomly locate 10,000 usersuniformly and find the serving sector and the set of interferences I foreach user. The following table summarizes the rate R and its occurrence.Rate [kbps] Fraction of users 38.4 0.0002 76.8 0.0169 153.6 0.0875 307.20.2116 614.4 0.1749 921.6 0.0979 1228.8 0.1898 1843.2 0.0702 2457.60.1510

[0062] We choose the distribution of m as a function of R to maximizethe gain g given that α≧α₀ for various thresholds α₀. We show resultsfor different values of α₀. Although we get better results by reducingα, making α too small would have undesirable effects such as increasingnoise N by 1/α. We limit m to be less than or equal to 0, 10, 5, and 1for R=38.4, 76.8, 153.6, and 307.2, respectively. We set m=0 for R=38.4kbps because it does not affect the performance much due to its smallprobability of occurrence. For rates >307.2 kbps, we assume m=0. Thefollowing table shows optimized m(R)'s for various thresholds α₀. α₀{m(76.8), m(153.6), m(307.2) g-1 α 0.9 {1, 0, 0}  1% 0.93 0.8 {10, 0, 0} 7% 0.81 0.7 {2, 0, 1} 17% 0.71 0.6 {1, 1, 1} 24% 0.62 0.5 {0, 5, 1} 41%0.52 0.0 {10, 5, 1} 55% 0.42

[0063] For example, the final line of the table indicates that athroughput gain of 55% is possible if the number of sectors that areturned off for each of the three rates indicated at the top of the tableare respectively 10, 5, and 1. The average time during which sectors areturned off is 58%.

[0064] This result shows that turning off as many sectors as possibleresults in the best performance. The adaptive reuse scheme for 38.4 Kbpsusers does not change the above result much because they do not occuroften anyway, but increasing m for those users will improve their userexperience.

[0065] The following table summarizes how much gain is possible for eachrate when {10,5,1} is used for the m(R)'s. It shows that the adaptivereuse scheme can improve the throughput of low rate users by as much as352% even after the penalty due to silent periods. The improved ratesdivided by α are all within our valid approximation range. However, someusers may have highly improved rates that are outside our validapproximation range. Because these numbers already include the penaltythat we are not using all time slots, this throughput gain is the realgain in user's experience. Improved rate Throughput Original rate [kbps][kbps] gain 76.8 347 352% 153.6 513 234% 307.2 500  62%

[0066] Case II

[0067] For case II, q=q′=1

[0068] In this case, S and S′ become$S \approx {{E\lbrack \frac{\lambda}{N + I_{A}} \rbrack}\quad {and}\quad S^{\prime}} \approx {{E\lbrack \frac{\alpha\lambda}{N + {\beta ( {I_{A} - I_{m}} )}} \rbrack}.}$

[0069] Using the same assumptions as in the first case, we get

α=1/E[m+1]

[0070] and${g = \frac{E\lbrack {{\alpha\lambda}/{\beta ( {I_{A} - I_{m}} )}} \rbrack}{E\lbrack {\lambda/I_{A}} \rbrack}},$

[0071] where we assume β=α for R<=1.2288 Mbps and β=1 for R>1.2288 Mbpsbecause high rates do not benefit much from silent sectors and this willhave a more significant effect on the throughput gain than in the firstcase.

[0072] In this case, the maximum gain g of one is achieved when m isalways zero for all R. This means the adaptive reuse should not be usedfor this traffic model, which is intuitive because all rates are fair inthis case.

EXAMPLES

[0073] In this section, we discuss examples of an adaptive time reusescheme.

[0074] As shown in FIG. 4, the sector control arrangements 52 can beimplemented in software, firmware, or hardware running on a base station50. The sector control arrangements include sector controllers(schedulers) 40, 42, 44 that determine which users in a sector will beserved and provide control signals 54 that control the transmissionstate of the sector antennas 56, 58, . . . , 60.

[0075] Let Qi(R) be a set of sectors that ought to be turned off whenthe i-th sector 58 is transmitting to a user with rate R 61. Let R0denote a set of rates considered as low rates that need to be boosted byturning off some neighbor sectors. With respect to sector i, thescheduler 42 first determines to which user in the sector to give thenext time slot if it is available. If the rate R of the user to whom itwill give the time slot is in the set R0, then the scheduler for thatsector requests neighbor sectors, e.g., sector 56 in Qi(R) not toschedule any packet in the next slot if possible. The scheduler 42schedules a packet to the user 61 regardless of any message to turn offthe sector i it might receive from some other sectors.

[0076] Otherwise, if the rate R is not within the set R0, the schedulerfor the i-th sector waits for any request from neighbor sectors who havethe sector i in any of their sets Qj(R) for any neighbor sector j andany R. If there is no such request, the i-the sector schedules thepacket for the user.

[0077] Although FIG. 4 implies that the control of the sectors by thesector control arrangements and the sector controllers must occurlocally to the BS, the control of sectors can also be handled globallyas among different cells and sectors in different cells. Globalcoordination requires a fast means of communication among BS's, which isnot always possible. Local coordination is usually feasible because alldecisions are local to a BS.

[0078] As another simple example, the fixed reuse pattern example withthe reuse factor of three can be modified to produce an adaptivepattern. Assume it is time for sector A to transmit while the other twosectors in the cell are forced to remain silent. Instead of turning offall the other sectors, we may want to allow some of these sectors totransmit at times when the transmission rate in sector A is higher thana threshold, provided that the requested transmission rates of othersectors are also higher than some other thresholds.

[0079] Other implementations are within the scope of the followingclaims. For example, the transmission power in some sectors might bereduced rather than being shut off completely in a celluar system wherethe transmission power can be controlled.

1. A method comprising in a cell of a cellular wireless communicationsystem, altering the SIR of at least one user in a sector of the cell bytemporarily reducing transmissions on a forward link in at least oneother sector of the cell or a sector in another cell in accordance witha pattern.
 2. The method of claim 1 in which the pattern is organized ina sequence of time slots and the pattern defines which of the sectorshas transmissions turned on or off in each of the time slots.
 3. Themethod of claim 1 in which the pattern comprises a predetermined fixedpattern that is repeated as time passes.
 4. The method of claim 1 alsoincluding determining a current state of transmissions in at least oneof the sectors of the cell or a sector in another cell, and setting thepattern dynamically based on the determined state of the transmissions.5. The method of claim 4 in which the current state of transmissionsincludes the scheduling status of transmissions in neighboring sectorsin the cell or in one or more other cells
 6. The method of claim 5 inwhich the current state of transmissions includes the transmission ratesof some neighbor sectors.
 7. The method of claim 4 in which the currentstate of transmissions includes the next time slot usage.
 8. The methodof claim 4 in which the current state of transmissions includes theforward link SIR.
 9. The method of claim 4 in which the current state oftransmissions includes user location.
 10. The method of claim 4 in whichthe current state of transmissions includes a fairness setting.
 11. Themethod of claim 4 in which the current state of transmissions includesan application type of user or QoS.
 12. The method of claim 1 in whichtemporarily reducing the transmissions comprises turning transmissionson and off in selected sectors according to the pattern.
 13. The methodof claim 12 in which the pattern includes turning off transmissions inother sectors more frequently to help users having lower communicationrates.
 14. The method of claim 1 also including arranging a frequencyreuse factor of one or higher in the wireless system.
 15. The method ofclaim 1 in which the wireless system comprises 1xEV-DO.
 16. Apparatuscomprising wireless transmission facilities for more than one sector ofa cell, and control facilities connected to the wireless transmissionfacilities and configured to alter the SIR of at least one user in asector of the cell by temporarily reducing transmissions on a forwardlink in at least one other sector of the cell or a sector in anothercell in accordance with a pattern.
 17. The apparatus of claim 16 inwhich the control facilities comprise sector controllers for controllingthe wireless transmission facilities for the respective sectors.
 18. Amedium bearing intelligence configured to enable a machine to effect theactions that comprise: in a cell of a cellular wireless communicationsystem, altering the SIR of at least one user in a sector of the cell bytemporarily reducing transmissions on a forward link in at least oneother sector of the cell or a sector in another cell in accordance witha pattern.
 19. Apparatus comprising a sector controller adapted tocontrol transmissions in a sector of a cell of a wireless communicationsystem and to communicate with other sector controllers in the cell orin one or more other cells to coordinate the turning on and off oftransmissions in at least one of the sectors based on the transmissionstate in at least another one of the sectors.